﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Foggy.Converters
{
    using System.Windows;
    using System.Windows.Data;

    /// <summary>
    /// Workaround for a bug in the WPF DataGrid (WPF Toolkit version).
    /// </summary>
    /// <remarks>The WPF DataGrid (WPF Toolkit version) throws a FormatException if a view model
    /// includes a SelectedItem property. This value converter works aroun that bug. The value
    /// converter is taken from Nigel Spencer's Blog, which identifies the bug and provides this
    /// solution. See: http://blog.spencen.com/2009/04/30/problems-binding-to-selectedvalue-with-microsoftrsquos-wpf-datagrid.aspx?results=1(</remarks>
    public class IgnoreNewItemPlaceHolderConverter : IValueConverter
    {
        /// <summary>
        /// New item placeholder name
        /// </summary>
        private const string NewItemPlaceholderName = "{NewItemPlaceholder}";

        /// <summary>
        /// Converts a value.
        /// </summary>
        /// <param name="value">The value produced by the binding source.</param>
        /// <param name="targetType">The type of the binding target property.</param>
        /// <param name="parameter">The converter parameter to use.</param>
        /// <param name="culture">The culture to use in the converter.</param>
        /// <returns>
        /// A converted value. If the method returns null, the valid null value is used.
        /// </returns>
        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            return value;
        }

        /// <summary>
        /// Converts a value.
        /// </summary>
        /// <param name="value">The value that is produced by the binding target.</param>
        /// <param name="targetType">The type to convert to.</param>
        /// <param name="parameter">The converter parameter to use.</param>
        /// <param name="culture">The culture to use in the converter.</param>
        /// <returns>
        /// A converted value. If the method returns null, the valid null value is used.
        /// </returns>
        public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            if (value != null && value.ToString() == NewItemPlaceholderName)
            {
                value = DependencyProperty.UnsetValue;
            }

            return value;
        }
    }
}